1. Field of the Invention
This invention relates to apparatus having finder optical systems, and more particularly to apparatus having finder optical systems for exhibiting both focus and composition for a photographic lens, while the correction of parallax between the lens and the finder and the shift of a range finding area displayed by a liquid crystal unit.
2. Description of the Prior Art
In a conventional apparatus having a finder optical system arranged independently of a photographic optical system for still photography, 8 mm cinematography, VTR or the like, the photographic viewfield frame and the finder viewfield frame did not exactly coincide with each other, so that the so-called parallax is produced, and the rangefinder spot in the field of view of the finder is shifted. This results in disadvantages while shooting.
The correction of the parallax has been made in various ways. For example, the photographic camera which has a reverse-Galilean type finder optical system with a half mirror positioned in a space between the objective lens and eye-piece to display a frame for the lens in the field of view of the finder, or a so-called mark finder, makes use of a photographic field of a movable view frame plate arranged near the focal point of the eyepiece to effect correction of the parallax. This moving mechanism is generally complicated. Also in application to auto-focus cameras, the correction of parallax must be carried out mechanically in a short time, depending upon the focusing position of the objective lens, and, therefore, a mechanism for performing this tends to be complicated.
With a compact zoom lens-equipped camera having a finder optical system in isolation from the photographic optical system another problem arises. That is the parallax due to the difference between the locations of the objective lens and the finder increases rapidly in particular as the focal length and the object distance become short. This makes it more difficult for the photographer to compose his picture and focus the lens with high accuracy.
To correct the parallax, for example, an additional frame for use in focusing down to shorter object distance may be provided in the finder. Another method is to use a mask plate arranged in the finder to move in automatic response to change in the object distance. However, the former is much too simple to effect sufficient correction. The latter has the drawback that the control mechanism for the mask plate assumes a very complicated form. In addition thereto, as the frame changes its position to correct the parallax, range finding area is also shifted. It is, therefore, necessary to correct this shift of the range finding area.
An example of an apparatus having finder optical systems which have made correction of the parallax, appears in U.S. Pat. No. 3,534,672 and German Pat. No. 11 450 10.